A Long Term Evolution (LTE) communication system uses several channels for transferring voice and data over a network. LTE utilizes Multiple Input Multiple Output (MIMO) antenna technology and is developed to improve spectral efficiency, distance coverage, and operational costs. A LTE equipment providing network within a cell is installed over a Base Transceiver Station (BTS) or an eNodeB. A mobile device communicates with the BTS using several channels present in the LTE standard. For establishing a communication session, a receiver of the LTE equipment receives a signal from the mobile equipment. Further, the LTE receiver processes the received signal to achieve synchronization with the mobile device and thus establish a successful communication session.
FIG. 1 illustrates a conventional receiver architecture used in the LTE communication system. Received samples of a signal received by a receiver are provided to a Single Carrier-Frequency Division Multiple Access (SC-FDMA) receiver unit. The SC-FDMA receiver unit extracts SC-FDMA symbols from the received samples. Further, the SC-FDMA receiver unit discards cyclic prefixes of the SC-FDMA symbols to derive useful parts of the SC-FDMA symbols. The SC-FDMA receiver unit reverses a half-subcarrier shift performed at a transmitter station and applies a Discrete Fourier Transform (DFT) on the useful part of each of the SC-FDMA symbols in order to derive a PUxCH resource grid. The PUxCH resource grid is used by a Physical Uplink Shared Channel (PUSCH) receiver, a Physical Uplink Control Channel (PUCCH) receiver, and a Sounding Reference Signal (SRS) receiver. The PUSCH is used as an LTE uplink data channel and the PUCCH is used as an LTE uplink control channel. Further, the SRS is periodically transmitted by a terminal to a base station for uplink channel quality estimation and for maintaining synchronization, once achieved using a Physical Random Access Channel (PRACH). The conventional receiver unit also includes a functionality of frequency and timing error correction, as exemplified in the FIG. 1.
For initially achieving synchronization between a terminal and the base station, the PRACH is used. In one case, the received samples and a FFT of the useful part of the SC-FDMA symbols are provided to a PRACH receiver, in order to achieve the synchronization. In another case, only the received samples may be provided to the PRACH receiver for achieving the synchronization. Necessary signal information derived by the PUSCH receiver, the PUCCH receiver, the SRS receiver, and the PRACH receiver is provided to a second layer (Layer 2) of the LTE communication system.
FIG. 2 illustrates a block representation of a conventional method for detecting PRACH preambles in a LTE communication system. Further, FIG. 2 explains the conventional method using the received samples and the FFT of the useful part of the SC-FDMA symbols. A signal received by a base station comprises a Cyclic Prefix (CP) and a PRACH preamble sequence part, at step 202. The PRACH preamble sequence part (assumed not including any delay) is segmented into a plurality of segments having uniform sizes, at step 204. In one case the PRACH preamble sequence part may be segmented into 12 segments represented by a=0 to a=11. Successively, a half-carrier shift and a Discrete Fourier Transform (DFT) may be performed on each of the 12 segments to generate frequency domain segments corresponding to the 12 segments, at step 206.
Subsequent to generation of the frequency domain segments, PRACH frequency segments are generated by selecting PRACH frequency locations from the frequency domain segments. The PRACH frequency segments are serially concatenated, at step 208. A Discrete Fourier Transform (DFT) operation is performed on 1536 points of the serially concatenated segments, at step 210. An output of the FFT operation is correlated, at step 214, with 839 points of predetermined references shown at step 212. A correlation product is thus generated at step 216. Subsequently, an Inverse Discrete Fourier Transform (IDFT) is performed on 1536 points of the correlation product to detect the PRACH preamble and its timing advance, at step 218.
Thus, the conventional technique for detecting the PRACH preambles uses many transformations of the signal between time-domain and frequency-domain. Further, 1536-point IFFT is performed on the correlation product to detect the PRACH preambles. Thus, the processing done using the conventional technique requires a lot of computations being performed at the base station, resulting in high computational complexity.